Dewaterers for fiber pulp suspensions

ABSTRACT

A pressure actuated dewatering device for a fiber pulp suspension having an elongated container with an inlet and an outlet for the suspension and a motor driven stirrer. The container wall includes separate sets of perforations each set communicating with a compartment located externally of the container and each compartment communicating through one-way valve with a common discharge conduit having a valve-controlled outlet for the drainage of water pressed from the suspension. A motor driven conveyor may be provided to carry the suspension having a higher concentration of fiber pulp away from the outlet. The driving motor of either the stirrer or the optional conveyor actuates a power control relay which emits pulses to a motor actuating the valve in the discharge conduit to control the pressure in the compartment thus regulating the amount of water removed from the suspension and consequently the concentration of fiber pulp in suspension as it passes through the outlet.

United States Patent Reinhall 1151 3,682,444 1 Aug. 8, 1972 [54]DEWATERERS FOR FIBER PULP SUSPENSIONS [72] Inventor: Rolf Berti]Reinhall, Lidingo,

Sweden [73] Assignee: Detibrator Aktiebolag, Stockholm,

Sweden [22] Filed: July 1, 1970 [21] Appl. No.: 51,419

Related US. Application Data [63] Continuation-impart of Ser. No.675,183, Oct.

13, l967, abandoned.

52 u.s.c1. ..259/6 51 1111. C1. morn/20 58 Field ofSearch....259/9,10,154, 149,169, 170,

[56] References Cited I UNITED STATES PATENTS 2,452,142 10/1948 Pecker..137/92 2,498,876 2/ 1950 Bowen ..l37/92 2,815,763 12/1957 Fanselow..l37/92 2,880,654 4/1959 Henry ..137/92 Primary Examiner-Robert W.Jenkins Attorney-Munson & Fiddler ABSTRACT A pressure actuateddewatering device for a fiber pulp suspension having an elongatedcontainer with an inlet and an outlet for the suspension and a motordriven stirrer. The container wall includes separate sets ofperforations each set communicating with a compartment locatedexternally of the container and each compartment communicating throughone-way valve with a common discharge conduit having a valve-controlledoutlet for the drainage of water pressed from the suspension. A motordriven conveyor may be provided to carry the suspension having a higherconcentration of fiber pulp away from the outlet. The driving motor ofeither the stirrer or the optional conveyor actuates a power controlrelay which emits pulses to a motor actuating the valve in the dischargeconduit to control the pressure in the compartment thus regulating theamount of water removed from the suspension and consequently theconcentration of fiber pulp in suspension as it passes through theoutlet.

10 Claims, 2 Drawing Figures PAYENIEmus 8 m2 ow mm 9 g @m 4 mm mm 4. ww8 cm N1 6 i 0000. o... mm mm g a 4m n S W Om m 0.1.0000 m mm w u u an.unook fi m 0..

L mM NH E 5 n L 0 TUE 5 6 X film/50m ATTORNEY DEWATERERS FOR FIBER PULPSUSPENSIONS suspensions and more particularly to pressure actuateddewatering devices.

Briefly, the dewaterer of the present invention is in the form of arelatively long container provided with inlet and outlet means for thesuspension and a stirrer driven by an electric motor. Separate sets ofperforations are provided in the wall of the container, each set ofperforations communicating with a compartment located externally of thecontainer for drainage of water pressed out of the fiber pulp suspensionin the container. The compartments communicate through separate one-wayvalves with a common discharge conduit provided with a control valve.The pressure in the compartments is regulated but maintained lower thanin the container to control drainage of water pressed out of the fiberpulp suspensions through the perforations. The suspension is preferablyintroduced under superatmospheric pressure into the container such as bymeans of a pump.

The dewaterer optionally may be provided with a power driven conveyorfor conveying the suspension having a higher concentration away from theoutlet for further processing as for example in a grinding apparatus.

In one embodiment of the present invention the motor driving the stirreroperates a power control relay which emits electrical impulses to amotor actuating the valve in the discharge conduit so that the pressurein the compartments is adjusted to a value corresponding to thepredetermined concentration of fiber pulp in the suspension in thecontainer. The power required to operate the stirrer as sensed by thepower control relay will be proportional to the concentration of solidfiber pulp in the suspension. V

In another embodiment, the motor driving the optional conveyor forconveying the suspension away from the outlet operates a power controlrelay for transmitting electrical impulses to the motor actuatingthedischarge conduit valve. The power required to operate the conveyor isproportional to the concentration of solid fiber pulp in the suspensioncarried by the conveyor.

The dewatering device according to the present invention permits therapid conversion of a pumpable pulp suspension to a highly concentratedpulp mass suitable for further treatment such as in a grindingapparatus.

One main object of the invention is to provide a dewaterer which iscapable of maintaining the concentration of the fiber pulp at apredetermined level with only small deviations. Thus, the dewaterer mustbe capable of responding rapidly to every such deviation to maintain thefiber pulp concentration constant.

Another object of the invention is to provide a de- 1 waterer having alarge capacity relative to its overall dimensions.

Further objects and advantages of the invention will become apparentfrom the following description considered in connection with theaccompanying drawings which form part of this specification wherein:

FIG. 1 shows diagrammatically and in vertical section apressure-operated dewaterer combined with a grinding apparatus; and

FIG. 2 shows diagrammatically a fragmentary view of a modification inthe dewaterer of FIG. 1.

Referring to FIG. 1, reference numeral 10 generally denotes apressure-operated dewaterer and 12 a grinding apparatus such as arefiner of the disc-type. The dewaterer comprises an elongatedvertically extending cylindrical container 14 which at its bottom oroutlet connects with an inlet 16 of the grinding apparatus 12. Thecylindrical container 14 is provided with separate sets of perforationsin the wall thereof, the separate sets being spaced from each otheralong the length of the cylindrical container. A further cylindricalwall 28 is located concentrically and externally of the container 14 anda series of annular partitions 62 extend between the interior ofcylindrical wall 28 and the exterior of the cylinder 14 to define aplurality of annular compartments 64, each compartment being associatedwith a different set of perforations 24. Each of the compartments 64communicates through a pipe 66 having a one-way valve 68 with a commondischarge conduit 30 having a control valve 32 which is adapted to beactuated by a motor 34 to control adjustment of the valve opening.

A stirrer 36 comprising a shaft 38 having a plurality of inclined blades40 is located within the cylindrical container 14. The free ends of theinclined blades 40 contact the internal surface of the container walland operate as scraping members. The plurality of blades 40 extendingover substantially the total length of the container 14 serve to rakethe perforated wall of the container. The shaft 38 is driven by a motor42 which also actuates a power control relay 44.

A liquid suspension of preferably vegetable or lignocellulose containingfiber material which has been subjected to partial disintegrationthrough digestion, defibration or grinding is pumped from a container 46by pump 48 through a conduit 50 and valve 52 into the dewaterer device10. The suspension as fed into the dewaterer has a very low pulpconcentration and therefore may be easily pumped into the dewaterer.

In the dewaterer 10, part of the liquid is driven off through theperforations 24 into the compartments 64, the pressure in thecompartments being lower than that in the container 14. Pulp materialcollected on the interior wall of the cylindrical container is scrapedoff by the rotating blades 40 and is conveyed downwardly by thecontinuous stirring and scraping action of the blades 40. Thedewateredpulp passes from the outlet of the dewaterer 10 into the inlet 16 of thegrinding apparatus 12 where the pulp is conveyed towards the grindingdiscs 18 and 20 by screw conveyor 54 driven by motor 56. Theconcentrated pulp suspension is fed between the grinding discs 18 and 20where a further disintegration of the pulp into individual fibers andpossibly also fibrillation is effected. Superatmospheric pressure ismaintained in the grinding apparatus 12 as in the dewaterer 10. Theground pulp is discharged through conduit 58 having a valve 60 forfurther treatment which is not described here as it falls outside thescope of the present invention.

The power control relay 44 transmits signals over a conductor 58 whichserve to actuate the motor 34 to 3 control the opening and closing ofvalve 32 in response to the concentration of pulp in container 14. Ifthe concentration of pulp at any moment exceeds the predetermineddesired level the stirrer 36 will meet increased resistance againstrotation. The power required to operate motor 42 will be increasedbecause of the increased resistance against rotation in the container,and this increase in required power will be sensed by the control relay44 which in turn will transmit a signal to the motor 34 causing thevalve 32 to be moved towards the closed position. This results in apressure rise in the discharge conduit 30 and the compartments 64whereby the pressure drop between the container 14 and the compartments64 is reduced, thereby reducing the rate of dewatering of i thesuspension. Consequently, more water will remain in the container 14 andthe concentration of the pulp therein will be reduced until thepredetermined level of concentration has been reached again. Conversely,if the dilution of the pulp suspension in the container 14 becomes toogreat, the resistance against rotation of the stirrer 34 is reducedcausing the control relay 44 to transmit signals opening the valve 32 sothat the rate of dewatering mayv be increased.

FIG. 2 shows an alternative form of the present invention wherein thoseparts of the apparatus common with FIG. 1 have been given the samenumerical designations. Here, however, a power control relay 44' similarto the power control relay 44 shown in FIG. 1 is actuated by the motor56 which operates conveyor 54. It will be readily appreciated that theconveyor 54 is subjected to a resistance from the pulp suspensionproportional to the concentration of pulp in the suspension as it isbeing conveyed. Thus, if the concentration of pulp is above apredetermined level, the increased power required in motor 56 requiredas a result of the increased resistance is detected by the relay 44'which in turn transmits signals through conductor 62 to the motor 34moving valve 32 towards the closed position to reduce the rate ofdewatering and thereby reduce the concentration of pulp in the dewateredsuspension as it is conveyed by conveyor 54. Conversely, if the pulpconcentration in the suspension conveyed by conveyor 54 falls below apredetermined value, the power control relay 44 will cause the valve 32to be opened increasing the dewatering rate whereby the pulpconcentration in the dewatered suspension is maintained at apredetermined value.

I claim: 7

1. A dewaterer for fiber pulp suspensions comprising a container havinginlet means and outlet means for feeding said pulp suspensiontherethrough, discharge conduit means for said container for dischargingof water from said suspension, valve means in said discharge conduitmeans for controlling the rate of liquid discharge, means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means in accordance with saiddetermination, whereby the pressure in said discharge conduit means isadjusted to maintain a predetermined pulp concentration in saidsuspension in said container, said discharge conduit means comprising aconduit containing said valve means, a plurality of perforations alongthe length of a wall of said container and passage means connecting saidperforations with said conduit.

2. A dewaterer as claimed in claim 1 wherein said passage meanscomprises a one-way valve means to prevent flow towards said container.

3. A dewaterer as claimed in claim 2 wherein said perforations aredivided into separate sets spaced along the length of the container andsaid passage means comprises a plurality of compartments, eachcompartment communicating with one set of said perforations and saidconduit, a one-way valve being positioned between each of saidcompartments and said conduit.

4. A dewaterer as claimed in claim 1 wherein said means for determiningthe proportion of pulp in said suspension in said container and forregulating said valve means comprises a rotatable stirrer in saidcontainer and means for detecting the power required to rotate saidstirrer which is proportional to the relative proportion of pulp is saidsuspension.

5. A dewaterer as claimed in claim 4 further comprising electric motormeans for driving said stirrer and a power control relay actuated bysaid motor for controlling said valve means.

6. A dewaterer as claimed in claim 5 wherein said stirrer comprises ashaft and a plurality of inclined blades attached to said shaft the freeends of said blades substantially contacting the internal surface of thecontainer wall to scrape pulp deposited on said wall.

7. A dewaterer for fiber pulp suspensions comprising a container havinginlet means and outlet means for feeding said pulp suspensiontherethrough, discharge conduit means for said container for dischargingof water from said suspension, valve means in said discharge conduitmeans for controlling the rate of liquid discharge, means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means in accordance with saiddetermination, whereby the pressure in said discharge conduit means isadjusted to maintain a predetermined pulp concentration in saidsuspension in said container, said means for determining the proportionof pulp in said suspension in said container and for regulating saidvalve means comprising conveyor means for conveying the dewateredsuspension away from said outlet means of the container and means fordetecting the power required to drive said conveyor which isproportional to the relative proportion in the said dewatered suspen-$1011.

8. A dewaterer as claimed in claim 7 further comprising electric motormeans for driving said conveyor and a power control relay actuated bysaid motor for controlling said valve means.

9. A dewaterer for fiber pulp suspensions comprising a container havinginlet means and outlet means for feeding said pulp suspensiontherethrough, discharge conduit means for said container for dischargingof water from said suspension, valve means in said discharge conduitmeans for controlling the rate of liquid discharge, means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means inaccordance with saiddetermination, whereby the pressure in said discharge conduit means isadjusted to maintain a predetermined pulp concentration in saidsuspension in said container,

a refiner for said pulp and feeding means for delivering said dewateredsuspension from the outlet means of said container to said refiner.

regulating said valve means in accordance with said determination,whereby the pressure in said discharge conduit means is adjusted tomaintain a predetermined pulp concentration in said suspension in saidcontainer, said outlet means includes means for refining said pulp andfeed means for delivering said dewatered suspension to said refiningmeans.

1. A dewaterer for fiber pulp suspensions comprising a container havinginlet means and outlet means for feeding said pulp suspensiontherethrough, discharge conduit means for said container for dischargingof water from said suspension, valve means in said discharge conduitmeans for controlling the rate of liquid discharge, means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means in accordance with saiddetermination, whereby the pressure in said discharge conduit means isadjusted to maintain a predetermined pulp concentration in saidsuspension in said container, said discharge conduit means comprising aconduit containing said valve means, a plurality of perforations alongthe length of a wall of said container and passage means connecting saidperforations with said conduit.
 2. A dewaterer as claimed in claim 1wherein said passage means comprises a one-way valve means to preventflow towards said container.
 3. A dewaterer as claimed in claim 2wherein said perforations are divided into separate sets spaced alongthe length of the container and said passage means comprises a pluralityof compartments, each compartment communicating with one set of saidperforations and said conduit, a one-way valve being positioned betweeneach of said compartments and said conduit.
 4. A dewaterer as cLaimed inclaim 1 wherein said means for determining the proportion of pulp insaid suspension in said container and for regulating said valve meanscomprises a rotatable stirrer in said container and means for detectingthe power required to rotate said stirrer which is proportional to therelative proportion of pulp is said suspension.
 5. A dewaterer asclaimed in claim 4 further comprising electric motor means for drivingsaid stirrer and a power control relay actuated by said motor forcontrolling said valve means.
 6. A dewaterer as claimed in claim 5wherein said stirrer comprises a shaft and a plurality of inclinedblades attached to said shaft the free ends of said blades substantiallycontacting the internal surface of the container wall to scrape pulpdeposited on said wall.
 7. A dewaterer for fiber pulp suspensionscomprising a container having inlet means and outlet means for feedingsaid pulp suspension therethrough, discharge conduit means for saidcontainer for discharging of water from said suspension, valve means insaid discharge conduit means for controlling the rate of liquiddischarge, means for determining the proportion of pulp in saidsuspension in said container and for regulating said valve means inaccordance with said determination, whereby the pressure in saiddischarge conduit means is adjusted to maintain a predetermined pulpconcentration in said suspension in said container, said means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means comprising conveyor means forconveying the dewatered suspension away from said outlet means of thecontainer and means for detecting the power required to drive saidconveyor which is proportional to the relative proportion in the saiddewatered suspension.
 8. A dewaterer as claimed in claim 7 furthercomprising electric motor means for driving said conveyor and a powercontrol relay actuated by said motor for controlling said valve means.9. A dewaterer for fiber pulp suspensions comprising a container havinginlet means and outlet means for feeding said pulp suspensiontherethrough, discharge conduit means for said container for dischargingof water from said suspension, valve means in said discharge conduitmeans for controlling the rate of liquid discharge, means fordetermining the proportion of pulp in said suspension in said containerand for regulating said valve means in accordance with saiddetermination, whereby the pressure in said discharge conduit means isadjusted to maintain a predetermined pulp concentration in saidsuspension in said container, a refiner for said pulp and feeding meansfor delivering said dewatered suspension from the outlet means of saidcontainer to said refiner.
 10. A dewaterer for fiber pulp suspensionscomprising a container having inlet means and outlet means for feedingsaid pulp suspension therethrough, discharge conduit means for saidcontainer for discharging of water from said suspension, valve means insaid discharge conduit means for controlling the rate of liquiddischarge, means for determining the proportion of pulp in saidsuspension in said container and for regulating said valve means inaccordance with said determination, whereby the pressure in saiddischarge conduit means is adjusted to maintain a predetermined pulpconcentration in said suspension in said container, said outlet meansincludes means for refining said pulp and feed means for delivering saiddewatered suspension to said refining means.